The present invention relates generally to methods and systems for providing a portable communication unit with a predetermined identification (ID) code to enable it to communicate with a base unit having a corresponding ID code, and more particularly to a method and system for providing a portable communication unit with an ID code through modulation of battery charging current.
Presently, there exist a variety of communication systems in which one or more battery operated portable units communicate with a central base station unit. Examples of such systems include portable telephone systems, garage door opener and remote computer terminals which communicate with a master computer. In such systems, and particularly in those wherein a number of portable units communicate with a base unit by means of radio signals, it is desirable that each portable unit communicates only with a given base unit, and similarly that each base unit communicates only with a specified group of portable units. This is particularly true where a number of radio communication systems operate on a shared frequency and communications are intended for only specified ones of the many portable units tuned to the common frequency. Numerous systems for providing such limitations have been developed and typically involve storing an electronic ID code in both the base unit and the portable units and then checking fo correspondence between the codes thus stored prior to establishing a communications link.
With such communications systems, it is necessary to encode each portable unit of the system so that the codes stored therein correspond to that stored in the system base station unit. A variety of code storage techniques have been developed including providing the units with hard-wired circuitry for generating a code, providing each unit with a removable programmable ID storage element or "code plug", or providing each unit with memory circuitry into which a user manually enters a code prior to use.
Each of these methods has drawbacks which adversely affect the effectiveness of the communication system. For example, the use of hard-wired circuitry to generate a code requires each unit to be individually wired in a unique manner which greatly increases manufacturing costs. Similarly, the use of code plugs requires each code plug to be uniquely programmed prior to its installation in a communication unit. When manual programming of each unit is provided, generally only a relatively few user-selected codes are available in order to avoid excessive manufacturing costs. Accordingly, the provision of relatively few available ID codes increases the likelihood that other users could accidentally or intentionally select the same codes, thereby compromising the security of the communication system. A further drawback of such systems is that when it is desired to purchase either a new base unit or portable unit for use in an existing system, it is necessary for either the manufacturer or the purchaser to assure that the unit obtained contains the proper code for allowing communication with other units of the system.
The present invention is directed to a method and apparatus for automatically transferring an ID code from a given base station unit to any compatible portable unit for storage therein when the portable unit is conductively mated with the base unit such as during battery charging. The system has the advantage that any compatible portable unit may thus be used with any base unit without the need for manually altering circuit components or manually programming the portable unit. Since it is necessary to mate each intended portable unit with the base station prior to allowing remote communication between the units, security of the system is maintained. Furthermore, the system provides a great deal of flexibility since a user may program as many or as few portable units as is necessary to meet his needs at any given moment.
In one such system in which a base unit provides an ID code to a portable unit, a third conductor, dedicated to transferring ID code information, was provided in addition to the two conductors needed to charge the battery of the portable battery. This system is described in the copending application of George C. Hawkins, entitled "Portable Telephone ID Code Transfer System", Ser. No. 558,738, filed Dec,. 5, 1983, and assigned to the assignee of the present invention. The present invention avoids the necessity for such an additional conductor since the present system relies on modulation of battery charging current in order to transfer ID code information. Elimination of the third conductor reduces manufacturing costs and offers greater flexiblity since compatibility with standard connectors presently in use can be retained.
In view of the foregoing it is a general object of the present invention to provide a new and improved electronic system wherein a base station unit communicates with one or more portable units.
It is a more specific object of the present invention to provide such an electronic system wherein the base station unit provides ID code information to the portable units.
It is a still more specific object of the present invention to provide a system wherein a base station unit provides ID code information to a portable unit without the need for modifying existing battery charging interconnections.